The present invention relates generally to heating and cooling systems, and particularly to a self-optimizing device to improve their efficiency.
In many areas of the world, temperature conditions exist in which humans cannot live comfortably and/or machinery cannot function properly without the supply of artificial cooling, and in particular, artificial heat to their immediate surroundings. In these areas, boilers, typically fueled by oil or gas, are often employed to provide this artificial heat as well as a supply of hot water.
Boiler manufacturers are chiefly concerned that their boilers are able to provide adequate artificial heat during the most extreme cold temperatures known in regions in which the heating equipment is sold. With few exceptions, however, most users never experience such extremely cold temperatures, or only experience them rarely, while more typically experiencing mildly cool temperature conditions (such as fifty degrees Fahrenheit, for example) that nonetheless require artificial heat, and they use the same boiler to provide artificial heat under these disparate temperature conditions. Similarly, those who purchase boilers, such as builders or those responsible for maintaining heating systems in commercial or residential buildings, tend to over-specify the requirements of their heating systems so that the systems will be more than effective under the coldest possible conditions. As a direct consequence boilers are almost always over-dimensioned for the typical conditions in which they are employed. This, in turn, results in the boilers having a low operating efficiency under normal operating conditions.
In a typical heating system, a boiler is used to heat a heating medium (water, for example) which is used to transfer heat to the environment to be heated. As the heating medium transfers heat, its temperature dropsxe2x80x94the rate at which its temperature drops varying with the thermal load on the heating system. When the temperature of the heating medium drops to a predetermined minimum value, the boiler turns on (initiating a boiler xe2x80x9con-timexe2x80x9d) to raise the temperature of the heating medium. The boiler then raises the temperature of the heating medium until it reaches a predetermined maximum level, at which time the boiler shuts off (completing the boiler on-time and initiating a boiler xe2x80x9coff-timexe2x80x9d). As the thermal load on the heating system drives down the temperature of the heating medium to the predetermined minimum, the boiler turns on (completing the boiler off-time and initiating a new boiler on-time) and the heating cycle repeats.
U.S. Pat. No. 5,470,019 to M{dot over (a)}rtensson (which is hereby incorporated herein by reference) addresses the problem of inefficiency due to boiler over-dimensioning by providing a boiler with improved efficiency based on a modification of the off-time of the boiler. The M{dot over (a)}rtensson boiler includes a microprocessor, which measures the off-time and multiplies that time amount by a predetermined, inputted number (a multiplying factor) less than or equal to one and stores the resulting time data measurement which it uses as a delay time to extend the off-time of the boiler. That is, when the heating medium reaches its predetermined minimum temperature and the boiler is signaled to reactivate, the boiler will not be reactivated immediately. Rather, the microprocessor will delay the activation of the boiler for an amount of time equal to the calculated delay time.
Usage of the M{dot over (a)}rtensson device results in improved boiler efficiency as explained therein by reference to FIGS. 2-5. But, in order to improve boiler efficiency, the M{dot over (a)}rtensson device relies upon a manually-inputted, predetermined number, and continues to use that same number to determine the resulting time data measurement until the number is manually reprogrammed.
Therefore, while use of the M{dot over (a)}rtensson device improves boiler efficiency, in order to provide the improved boiler efficiency, an individual or individuals would require training as to how and when to program (or reprogram the multiplying factor in order to create (or alter) the calculated time delay of the M{dot over (a)}rtensson device. And, in order to achieve optimum boiler efficiency, one of these trained individuals may need to be present on a seasonal basis (for example) to reprogram the device with an optimal multiplying factor for given heating conditions.
Therefore, there is a need for a device or system that optimizes the efficiency of heating controllers such as the M{dot over (a)}rtensson device by making the controller self-calibrating and self-optimizing while requiring little or no human intervention. This need is particularly acute for boilers used in a residential setting where xe2x80x9chouse callsxe2x80x9d by trained technicians can be rather expensive.
The present invention provides a self-optimizing device and method for use with a thermal transfer system. Although the invention is primarily described as being applicable to one or more oil or gas fired boilers, it is understood that the invention has other applications as well, such as for use with air conditioners or other cooling systems.
An apparatus of the invention controls a heating unit in a manner so as to improve the energy efficiency of the heating unit using an autocalibration processor. The heating unit controlled by the controller of the invention employs a heating medium that is heated by the heating unit and which transfers the heat into an ambient atmosphere outside of the heating unit. The heating unit has an on-state initiated when a characteristic of the heating medium representative of the heating capacity of the medium decreases below a minimum level, and an off-state initiated when the characteristic of the heating medium reaches a maximum level.
The controller includes an input element, an output element, a time-measuring element, and a processor. The input element receives a signal from a sensor, the signal indicating the heating medium characteristic representative of the heating capacity of the heating medium. The output element signals the heating unit to begin its on-state. The time-measuring element measures an off-time, the off-time being the length of time from initiation of the off-state of the heating unit until the characteristic of the heating medium decreases below the minimum level. The processor determines a delay time and for signaling the heating unit to delay initiation of the on-state by the delay time amount, the extension of the off-time resulting in an energy savings over an undelayed initiation. The processor further comprising an autocalibration processor for determining a delay time that results in optimum energy savings.
In one embodiment, the autocalibration processor includes control logic for performing an autocalibration process that begins by measuring on-time and off-time components of a first on-off cycle of the heating unit. The autocalibration processor then selects a second on-off cycle for the heating unit having an off-time similar to (for example, having a length within 15% of) the off-time of the first on-off cycle of the heating unit. The autocalibration process next applies a first delay time prior to initiating a subsequent on-state and calculates an index corresponding to an energy savings for the first delay time. The autocalibration processor then selects a third on-off cycle for the heating unit having an off-time similar to the off-time of the first on-off cycle of the heating unit. A second delay time is then applied prior to initiating a subsequent on-state and an index corresponding to an energy savings for the second delay time is calculated. The autocalibration means can test any number of delay times, and preferable includes testing a delay time that is one hundred percent of the off-time of the first cycle. The autocalibration means then calculates a delay time that corresponds to an optimum energy savings. For example, the autocalibration processor can select a delay time corresponding to the highest energy savings index, or it can interpolate or extrapolate from the test data.
In another embodiment, the autocalibration means continuously calculates optimum economy settings. In this embodiment, the autocalibration means selects an initial economy factor for the processor. It then continuously records a parameter of the heating system corresponding to a thermal load on the system. Based on this parameter, the autocalibration means calculates an optimum economy factor and increments or decrements the processor economy factor in a direction toward the optimum economy factor. Preferably, the parameter is a moving average that covers a long enough time to filter out one day abnormal conditions, but is a short enough time that the average responds promptly to seasonal changes. In one implementation, the optimum economy factor is a delay time percentage that is calculated as optimum economy factor is calculated as Exe2x88x92(Axc3x97(E÷B)); where E is the maximum allowed economy factor, A is the parameter of the heating system corresponding to the thermal load on the system, and B is a maximum parameter of the heating system corresponding to the thermal load of the system.
By applying the apparatus or method of the invention, the operation of a heating system can be optimized with little or no human intervention. The apparatus can be a self contained controller having a user interface, or it can interface with a computer network using known computer communication means.